What is a Semi-Convex Edge?

The semi-convex edge is ground by first establishing a convex profile across most of the blade face using a curved grinding wheel, then finishing the final 0.5-1.0mm near the cutting apex on a flat stone or flat grinding surface. This creates a blade that is convex in cross-section through 80-90% of its width but terminates in a small flat bevel at the cutting edge itself. The flat section near the apex serves two purposes. First, it creates a more durable edge — the flat bevel provides a wider support angle behind the cutting point, meaning the steel has more material backing the edge and is less likely to chip or roll under impact. Second, it simplifies sharpening — the flat apex can be touched up on a standard whetstone without destroying the overall blade geometry, unlike a full convex edge which requires a rotating wheel to maintain its curve. Some manufacturers describe their semi-convex edges as "modified convex" or "hybrid convex." There is no standardized industry definition, so the exact grind geometry varies between brands. Joewell's semi-convex uses a broader flat section (approximately 1.0mm) for extra durability, while Matsuzaki's version keeps the flat to under 0.5mm, leaning closer to full convex performance. The trade-off is that the small flat section does create a subtle shoulder in the blade profile. During aggressive slide cutting, this shoulder can create slightly more friction than a true convex edge. However, for point cutting, blunt cutting, and light texturizing, the difference in feel is minimal for most stylists.